Grinding bur.



Patented Oct. 30, 1917.

/// IIIIHIIU) JOHN HOLLAND' nn'rzgor OnowNfroIN'r, INDIANA, AssIGNoR `'ro Tian LE'TZ iviANiIrAo-i i Tuning-COMPANY, or CROWN POINT, INDIANA, a CORPORATION OFINDIANA.- 1

eRINnING-,BUR

To all whom t may conoem Be it knownthat I, JOHN a citizen of the United States, and afesi'dent of Crown Point,"in the coiintyofliake and State of Indianahay,e invented certain new and useful Improvements Grr'inding-Bu'r's',`

' reference characters are usedl to designate eral outline, and preferably six in number..

identical parts in all the figures, of which,-

Figure 1 isa viewy of the grinding yface of abur embodying my invention;

Fig. 2 is a section on the line 2 2 of F ig.`

1; andy Fig.,3 is an enlarged view of a portion of the face of thefbur shown in Fig. A1. Y

The body of the bur preferably consists of a thin annular casting, which may be reinforced on its backby employing one or more annular ribs o. Its grinding surface is generally flat, except so far as itis broken by the grinding ribs to be described, which, it will be understood,`are preferably east integral with the body and ground olf on a flat stone so as to form cutting edges and grinding surfaces on all the ribs in the same plane, and adapted to eoperate withsimilar ridges and surfacessimilarly formed on the similar ribs on the opposed face of thecompanion bur.

The ribs are preferably arranged y in groups, substantially triangular in their gen- The ribs going to make upeach of the six groups have preferably they same design, or

substantially so, so that thedescription ofy one group will suiice for all of them` Considering an imaginary radial line, such as a central vertical line in Fig. 1 or 3, as the base line for the purposes of de-v scription, the main ribs a, b, c, CZ, e and f are parallel to each other and allv extend at an angle'y of substantially sixty degrees yto the base line. These ribs are, preferably jinterrupted at intervals, and thus consist of sections a, a', a2, a3, at, b, b', b2, b3, bt, c, o',

bae ribs gah .ki Z2 mijn: O7 pinguin sa It," l

between'the'main ribs extend at rightfangles thereto,`and are preferably connected to theA ends ofthe main-,ribsectionaeach of said sections havingy one'baflierib section attached" toeach end but extending in opposite directions therefrom. .'Ihese baffle-rib sections, as will be seen, are g, g', L, h,

a l 2 l g The baffle ribs connected to the lower ends of the main-rib sectionsk thus form with the next main-rib sections toward the center an angle with an opening at its apex andits sides converging in the direction of Inovement of the grain. The ribs are preferably designed solas to leave the plane triangular spaces 'w between each group.

In operation,4 the main-rib sections of yone blur cooperate with half of the baiiie-ribsections of the companion bur to shear the grain between their cutting edges in a manner that will be readily understood by those conversant vwith the use of these burs. The converging ribs forming the angles before describedy force the grain as it tends to move radially outward into the angles which force it upwardly fromv the faces of the burs so as to bring it into the shearing planes ofthe burs, so that before it reaches the peripheries of the burs all of it will be sheared and crushed. Thelhalf of the baille ribs that do not have any material shearing action `assist in forcing` the grain into the abovementioned angles and prevent its Imoving outwardly directly along the line of the main ribs.

What I claim as new, and desire to secure yby Letters Patent of the United States, is:

1. A grinding'bur consisting of a genf L a v` a 'es d i c' ertlly ii t disk ha in seri of gr nling ribs projectingtherefrom and havingtheir on substantially radial lines, some of the baie ribs serving to direct the finely ground grain to the more direct passages.

2. `A grinding bur consisting of a generally flat disk having a series of grinding t ribs projecting ltherefrom and having their flat top surfaces in the saine planey and forming shearing edges, saidv ribs bein'garranged in plural groups consisting of Vthe main parallel ribs extending at generallyy acute angles to radial lines, and short baffle ribs at substantially right angles to the mainr portions, said baffle ribs being oonneetedto,` the main ribs, one ateach end and extending Copies et this patent may be obtained for therefrom in 'opposite directions, both sets of ribs combining to ,form comparatively "Wide,z tortuous passages to the .periphery of Deeember,A. D. 1916.

JoHN HOLLAND LETZ. [n a] i Witness: g Y,

JOHN HOWARD MCELROL livel cents each, byra'ddressng the Commissioner of Patents. Washington, D. il. 

